Nonlinear, solid state devices that are bistable, that is, they have a high and low impedance state, are commonly referred to as thyristors. Thyristors may be switched from one impedance state to the other by means of a control signal. Unijunction transistors and PNPN diodes are common thyristors. Thyristors are not generally useful, however, where fast switching and high power pulses are required. They are known for their relatively long turn-on times (time required to reach peak voltage) and their even longer turn-off time (time required for the base region to be depleted of stored charge).
Unijunction silicon transistors (i.e., P+NN+ and P+PN+ diodes) have been made to operate in an avalanche, "trapped plasma" mode, see "A Theory For The High Efficiency Mode of Oscillation In Avalanche Diode," by Clorfiene et al., RCA Review (September, 1969), p. 397; and U.S. Pat. No. 3,612,914. The "trapped plasma" has been obtained by providing a relatively highly doped (about 1 .times. 10.sup.15 to 1 .times. 10.sup.16 atoms/cm.sup.3) and a narrow width (about 10 micron) base region. These devices provide highly efficient, high "Q" microwave oscillators (e.g., 700-800 M Hz), high speed switches and short duration pulse generators. However, such diodes do not have utility as high power devices.
A reverse switching rectifier has been developed for fast switching of high power, see U.S. Pat. No. 3,584,270. This device provides both short turn-on (di/dt) and short turn-off times. But even this specific thyristor is not sufficiently fast for uncompromising use in applications such as power sources for radar modulations, power sources for injection laser diodes, power sources for electro-optical switching and applications for laser triggering, where rapid, high power turn-on and turn-off times are required. For such applications, no solid state control device was heretofore available with fully satisfactory electrical characteristics. Instead, gas switch tubes such as thyratron tubes are generally used in such applications.
The present invention overcomes the difficulties and disadvantages of prior devices and provides a solid state device capable of ultrafast, high power switching and pulse generation.